Antonios G. Kanaras

Preparation of peptide functionalized gold nanoparticles using one pot EDC/sulfo-NHS coupling

Although carbodiimides and succinimides are broadly employed for the formation of amide bonds (i.e., in amino acid coupling), their use in the coupling of peptides to water-soluble carboxylic-terminated colloidal gold nanoparticles remains challenging. In this article, we present an optimization study for the successful coupling of the KPQPRPLS peptide to spherical and rodlike colloidal gold nanoparticles. We show that the concentration, reaction time, and chemical environment are all critical to achieving the formation of robust, peptide-coated colloidal nanoparticles. Agarose gel electrophoresis was used for the characterization of conjugates.

Highly sensitive DNA sensor based on upconversion nanoparticles and graphene oxide

In this work we demonstrate a DNA biosensor based on fluorescence resonance energy transfer (FRET) between NaYF4:Yb,Er nanoparticles and graphene oxide (GO). Monodisperse NaYF4:Yb,Er nanoparticles with a mean diameter of 29.1 ± 2.2 nm were synthesized and coated with a SiO2 shell of 11 nm, which allowed the attachment of single strands of DNA. When these DNA-functionalized NaYF4:Yb,Er@SiO2 nanoparticles were in the proximity of the GO surface, the π-π stacking interaction between the nucleobases of the DNA and the sp(2) carbons of the GO induced a FRET fluorescence quenching due to the overlap of the fluorescence emission of the NaYF4:Yb,Er@SiO2 and the absorption spectrum of GO. By contrast, in the presence of the complementary DNA strands, the hybridization leads to double-stranded DNA that does not interact with the GO surface, and thus the NaYF4:Yb,Er@SiO2 nanoparticles remain unquenched and fluorescent. The high sensitivity and specificity of this sensor introduces a new method for the detection of DNA with a detection limit of 5 pM.

Thioalkylated tetraethylene glycol: a new ligand for water soluble monolayer protected gold clusters.

Ligand-stabilised, water-soluble gold nanoparticles of two different size ranges (2-4 and 5-8 nm) are readily prepared using monohydroxy (1-mercaptoundec-11-yl) tetraethylene glycol as a novel capping agent. These nanoparticles are as stable as alkylthiol-capped monolayer protected clusters (MPCs) and do not aggregate from aqueous solution under a wide range of stringent conditions. It is expected that this new material will be useful for a number of bio-analytical applications.

Interactions of human endothelial cells with gold nanoparticles of different morphologies

The interactions between noncancerous, primary endothelial cells and gold nanoparticles with different morphologies but the same ligand capping are investigated. The endothelial cells are incubated with gold nanospheres, nanorods, hollow gold spheres, and core/shell silica/gold nanocrystals, which are coated with monocarboxy (1-mercaptoundec-11-yl) hexaethylene glycol (OEG). Cell viability studies show that all types of gold particles are noncytotoxic. The number of particles taken up by the cells is estimated using inductively coupled plasma (ICP), and are found to differ depending on particle morphology. The above results are discussed with respect to heating efficiency. Using experimental data reported earlier and theoretical model calculations which take into account the physical properties and distribution of particles in the cellular microenvironment, it is found that collective heating effects of several cells loaded with nanoparticles must be included to explain the observed viability of the endothelial cells.

Polymer-Enhanced Stability of Inorganic Perovskite Nanocrystals and Their Application in Color Conversion LEDs.

Cesium lead halide (CsPbX3, X = Cl, Br, I) nanocrystals (NCs) offer exceptional optical properties for several potential applications but their implementation is hindered by a low chemical and structural stability and limited processability. In the present work, we developed a new method to efficiently coat CsPbX3 NCs, which resulted in their increased chemical and optical stability as well as processability. The method is based on the incorporation of poly(maleic anhydride-alt-1-octadecene) (PMA) into the synthesis of the perovskite NCs. The presence of PMA in the ligand shell stabilizes the NCs by tightening the ligand binding, limiting in this way the NC surface interaction with the surrounding media. We further show that these NCs can be embedded in self-standing silicone/glass plates as down-conversion filters for the fabrication of monochromatic green and white light emitting diodes (LEDs) with narrow bandwidths and appealing color characteristics.

Shaping Supramolecular Nanofibers with Nanoparticles Forming Complementary Hydrogen Bonds

Functionalized gold nanoparticles with complementary H-bonding groups can control the secondary structure of xerogel fibers formed by a molecular conductor thanks to their incorporation into the nanowires, which show metal-like conductivity once doped without the need for annealing. The picture shows a photograph of the xerogel, TEM images of Au particles in the gel and a single fiber, and an AFM image revealing the texture of the gel.

Receptor-mediated interactions between colloidal gold nanoparticles and human umbilical vein endothelial cells.

A new strategy to manipulate cell operations is demonstrated, based on membrane-receptor-specific interactions between colloidal peptide-capped gold nanoparticles and human umbilical vein endothelial cells. It is shown that colloidal gold nanoparticles of similar charge and size but capped with different peptide sequences can deliberately trigger specific cell functions related to the important biological process of blood vessel growth known as angiogenesis. Specific binding of the peptide-capped particles to two endothelial-expressed receptors (VEGFR-1, NRP-1), which control angiogenesis, is achieved. The cellular fate of the functional nanoparticles is imaged and the influence of the different peptide-coated nanoparticles on the gene expression profile of hypoxia-related and angiogenic genes is monitored. The findings open up new avenues towards the deliberate biological control of cellular functions using strategically designed nanoparticles.

Laser-induced damage and recovery of plasmonically targeted human endothelial cells

Laser-induced techniques that employ the surface plasmon resonances of nanoparticles have recently been introduced as an effective therapeutic tool for destroying tumor cells. Here, we adopt a low-intensity laser-induced technique to manipulate the damage and repair of a vital category of noncancerous cells, human endothelial cells. Endothelial cells construct the interior of blood vessels and play a pivotal role in angiogenesis. The degree of damage and repair of the cells is shown to be influenced by laser illumination in the presence of gold nanoparticles of different morphologies, which either target the cellular membrane or are endocytosed. A pronounced influence of the plasmonic nanoparticle laser treatment on the expression of critical angiogenic genes is shown. Our results show that plasmon-mediated mild laser treatment, combined with specific targeting of cellular membranes, enables new routes for controlling cell permeability and gene regulation in endothelial cells.

Manipulation of in Vitro Angiogenesis Using Peptide-Coated Gold Nanoparticles

We demonstrate the deliberate activation or inhibition of invitro angiogenesis using functional peptide coated gold nanoparticles. The peptides, anchored to oligo-ethylene glycol capped gold nanospheres, were designed to selectively interact with cell receptors responsible for activation or inhibition of angiogenesis. The functional particles are shown to influence significantly the extent and morphology of vascular structures, without causing toxicity. Mechanistic studies show that the nanoparticles have the ability to alter the balance between naturally secreted pro- and anti-angiogenic factors, under various biological conditions. Nanoparticle-induced control over angiogenesis opens up new directions in targeted drug delivery and therapy.

Interaction of stable colloidal nanoparticles with cellular membranes

Due to their ultra-small size, inorganic nanoparticles (NPs) have distinct properties compared to the bulk form. The unique characteristics of NPs are broadly exploited in biomedical sciences in order to develop various methods of targeted drug delivery, novel biosensors and new therapeutic pathways. However, relatively little is known in the negotiation of NPs with complex biological environments. Cell membranes (CMs) in eukaryotes have dynamic structures, which is a key property for cellular responses to NPs. In this review, we discuss the current knowledge of various interactions between advanced types of NPs and CMs.